Uncertainty in fundamental period estimates leads to inaccurate design seismic loads.

To help engineers calculate design seismic loads, the 2005 edition of the National Building Code of Canada provides empirical equations to estimate the fundamental lateral period of a building. Unfortunately, these equations are inaccurate, so the fundamental period of a building once it is erected could be considerably different than the period used in design. In this study, we use experimental period data and uncertainty propagation to show that the uncertainty associated with the fundamental period significantly influences the accuracy of design seismic loads. When the period from the appropriate empirical equation is used in design, base shear may be considerably overestimated; while it may be considerably underestimated when the maximum period allowed by the code is used. Further, we show that the resulting uncertainty in base shear varies with location, seismic force-resisting system, site conditions, and building height. [ABSTRACT FROM AUTHOR]